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    <script>
        let chengji = (a, b) => {
            let ji = 1;
            for (let i = a; i <= b; i++) {
                ji *= i
            }
            return ji
        }

        let jicheng = (a, b) => {
            let add = 0;
            for (let i = a; i <= b; i++) {
                add += chengji(a, i)
            }
            return add
        }

        console.log(jicheng(1, 3))

    </script>
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